Ex vivo screen identifies CDK12 as a metastatic vulnerability in osteosarcoma
Ian Bayles, … , Rani E. George, Peter C. Scacheri
Ian Bayles, … , Rani E. George, Peter C. Scacheri
Published September 9, 2019
Citation Information: J Clin Invest. 2019;129(10):4377-4392. https://doi.org/10.1172/JCI127718.
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Research Article Genetics Oncology

Ex vivo screen identifies CDK12 as a metastatic vulnerability in osteosarcoma

Abstract

Despite progress in intensification of therapy, outcomes for patients with metastatic osteosarcoma (OS) have not improved in thirty years. We developed a system that enabled preclinical screening of compounds against metastatic OS cells in the context of the native lung microenvironment. Using this strategy to screen a library of epigenetically targeted compounds, we identified inhibitors of CDK12 to be most effective, reducing OS cell outgrowth in the lung by more than 90% at submicromolar doses. We found that knockout of CDK12 in an in vivo model of lung metastasis significantly decreased the ability of OS to colonize the lung. CDK12 inhibition led to defects in transcription elongation in a gene length– and expression-dependent manner. These effects were accompanied by defects in RNA processing and altered the expression of genes involved in transcription regulation and the DNA damage response. We further identified OS models that differ in their sensitivity to CDK12 inhibition in the lung and provided evidence that upregulated MYC levels may mediate these differences. Our studies provided a framework for rapid preclinical testing of compounds with antimetastatic activity and highlighted CDK12 as a potential therapeutic target in OS.

Authors

Ian Bayles, Malgorzata Krajewska, W. Dean Pontius, Alina Saiakhova, James J. Morrow, Cynthia Bartels, Jim Lu, Zachary J. Faber, Yuriy Fedorov, Ellen S. Hong, Jaret M. Karnuta, Brian Rubin, Drew J. Adams, Rani E. George, Peter C. Scacheri

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Figure 2

CDK inhibitors reduce metastatic cell outgrowth in the lung microenvironment.

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CDK inhibitors reduce metastatic cell outgrowth in the lung microenviron...
(A) Heatmap showing IC50 values for the CDK inhibitors tested, as determined by Selleck chemicals. NN, not determined. Concentrations tested for each compound are represented by the sizes of the squares within the boxes. Percentage death refers to the reduction of the GFP+ area in the compound vs. DMSO control–treated cells at low and high doses. The left side of the gray-red boxes corresponds to the percentage of cell death achieved with the low dose; the right side denotes the percentage of death achieved with the high dose. Right, compound concentrations and corresponding percentages of cell death achieved in a secondary assessment of 7 initial hits. (B) Top: representative GFP images of lung explants seeded with either MG63.3 or 143B cells and treated with the indicated CDK inhibitors for 14 days. Bottom: GFP-based quantification of lung explants from the respective cell line, treated with indicated compound. Data are presented as mean ± SD with at least 3 explants per condition. Ordinary 1-way ANOVA with Tukey’s multiple comparisons test was used to compare across groups. **P < 0.01. Original magnification, ×2. (C) Top: drawing of in vivo CRISPR CDK12 knockout experiment. Middle: quantification of GFP+ area of lungs from each mouse in the experiment. Four to five images were taken per set of lungs and quantified for GFP+ area using ImageJ. Filled dots indicate those in the representative images. Bottom: representative images from indicated lungs. Original magnification, ×2. Data are represented as mean ± SD. Ordinary 1-way ANOVA with Tukey’s multiple comparisons test was used to compare across groups. **P < 0.01.